The Hyatt Regency hotel walkways collapsed in 1981 due to errors in the structural engineering design. The original design had each walkway supported by a single rod, but the fabricator modified the design to use two rods for each walkway without properly communicating the changes. This placed twice the intended stress on structural nuts, causing them to deform and the walkways to collapse. The engineering company approved the redesign without thoroughly checking it, demonstrating issues with the communication and review processes between the companies involved.

1. Stephanie Ulman
Stephanie Ulman Hyatt Assignment 9/10/12
0610 403-02 Failure of Mechanics 1
Executive Summary
In Kansas City, Missouri in 1881 the Hyatt Regency Hotel walkways collapsed. There
are several reasons why the hotel walkways collapsed. One of the main reasons why
the walkways collapsed was that there were two supporting rods on the 2nd and 4th floor.
So these nuts were carrying twice the stress.
This stress caused a deformation in the structural nut and washer on the box beam
(joint). So therefore the joint could not hold twice the amount of stress. The box beam
began to separate causing the walkway to collapse.
Another reason is the communication between the companies G.E.C. and Havens Steel
was not very good because there was all of miscommunication between them. The FBD
below shows the structures of the original drawing and the modified drawing. The
drawing on the right is the original drawing and the drawing on the left is the modified
drawing.

2. Stephanie Ulman
Stephanie Ulman Hyatt Assignment 9/10/12
0610 403-02 Failure of Mechanics 2
Introduction
At Hyatt Regency Hotel the walkway collapsed in the year of 1981. There are several
reasons why the hotel walkway collapsed. One reason is that the communication
between the engineering and the fabricator was not very good. The engineer Jack D.
Gillum gave a sealed of approval was attached to the revised design of the design
drawings. One of the problems with the engineering drawing was that it had two
supporting rods. Therefore the nuts had twice the amount of stress on them. Another
reason why the building collapsed was because the washers and supporting nuts got
deformed. Daniel M. Duncan and Jack D. Gillum of G.C.E. where found guilty and
changed with gross negligence incompetence, misconduct and unprofessional conduct
and cannot practice their engineering services in two states.
NOTE: Research is also found in the problems
First Problem:
One of the reasons for the collapse of the hotel walkway was the engineering design.
The fabricator changed the design. Originally the design looked in the pictures below.
Figure 1 shows the diagram of the 2D drawing. Also, this design is the original design of
the walkways where suspended from the ceiling

3. Stephanie Ulman
Stephanie Ulman Hyatt Assignment 9/10/12
0610 403-02 Failure of Mechanics 3
Figure 2 shoes a 3D picture of the original drawing. The original drawing has only one
rod.
These are some of the things the original design had:
 Wide flange (overhang) beams that were used on either side of the walkway
upon which was hung a box beam.
 A clip angle welded to the top of the beam was connected to the flange beams
with bolts
 One end of the walkway was welded to a fixed plate while a sliding bearing
supported the other end
 The walkways were suspended from the ceilings by long rods.
 The rod would pass through the top walkway and on down to the bottom
walkway.
 Under each walkway, a load-carrying nut would be used on each of the rods to
carry the load of the walkway.
 The original design called for the nuts to be 30 feet up the rods, the entire length
of the rods had to be threaded. (Threading 30 feet rod is difficult and costly)
 The load of this design for each hanger rod was to be 90 kN.
The fabricator decided to change the original design to make it easier and less costly to
construct. The change in the design made the walkways in the hotel to collapse.

4. Stephanie Ulman
Stephanie Ulman Hyatt Assignment 9/10/12
0610 403-02 Failure of Mechanics 4
Figure 3 shows the 2D drawing of the changed design. This failed because there was
too much weight on the nuts.
Figure 4 shows a 3D drawing of the modified design that the fabricator designed. The
picture shows that two rods that are supporting a walkway. The two rods have nuts but
only one of the nuts is carrying the weight of two rods.
This drawing is a
2D drawing of the
design. This failed
because there was
too much weight
on the nuts.

5. Stephanie Ulman
Stephanie Ulman Hyatt Assignment 9/10/12
0610 403-02 Failure of Mechanics 5
The changes on this design were:
 The change in the design put a double load on the connector rod.
 One end of each support rod was attached to the atrium’s roof cross beams.
 The second rod was attached to the box beam 4 inches from the first rod
 They cut the rods in half and ran those halves from the roof to the top walkway
and placed nuts
 They threaded only about 6 inches of each end of each rod, a considerably
easier task.
 The load of this design was increased to 180 kN on the fourth floor box beam
connections
The FBD below explained (FBD is on pg 12-14)
The free body diagram below consists of the original design and the modified design.
In the FBD shows the forces remain equal. The weight of each nut changes in the FBD.
The right upper nut changes it has more stress on it than any other nut on the diagram.
(because this design is the modified design) This nut has to carry the weight of two
walkways.
How the hotel was designed:
The 2nd and 4th floor where designed with the modified design and the 3rd floor was
made by the original design. The 4th and 2nd floor was suspended together by the
ceiling. See diagram below.
Figure 5 shows how the walkways were attached. The 4th and 2nd floors were
suspended together.

6. Stephanie Ulman
Stephanie Ulman Hyatt Assignment 9/10/12
0610 403-02 Failure of Mechanics 6
The 3rd floor was suspended by the ceiling shown in the picture below.
Figure 6 shows the 3rd floor and how it was suspended by the ceiling. This walkway was
built with the original design.
The 4th floor was the walkway to collapse first. Since the 2nd and 4th floor where suspend
together the 4th floor caused the 2nd floor walkways to collapse too. The picture below
shows the 3rd walkway did not fall.
Figure 7 shows a picture of the 3rd floor walkway. The 3rd floor walkway did not collapse
only the 2nd and 4th floor collapsed.
As you can see in this
picture this is the 3rd
floor walkway. Also the
3rd
floor walkway did
not collapse only the
2nd
and 4th
floor
collapsed.

7. Stephanie Ulman
Stephanie Ulman Hyatt Assignment 9/10/12
0610 403-02 Failure of Mechanics 7
Figure 8 shows the 4th floor walkway and beam lying in the lobby of the hotel. (After the
walkway collapsed)
Second Problem
The box beam consisted of two square channels. A square channel is shown below.
These square channels were welded together.
Figure 9 shows a square channel.
One of the problems with welding them together it causes a heat affected zone. The
heat affected zone makes the steel more brittle. This was looked like when it was
welded together.

8. Stephanie Ulman
Stephanie Ulman Hyatt Assignment 9/10/12
0610 403-02 Failure of Mechanics 8
Figure 10 shows two squared channels that are welded together.
The fabricator also made changes in the box beam design as well. These are lists of the
original design and the changed design.
Original box beam design:
 The ends of the box beams were then drilled to receive the rods.
 The box beam consisted of two 8 x 8.5 MC channels
 The beams consisted of two 8-inch channel sections welded toe to toe to make
up a box beam.
 Each box beam of the walkway was supported by a washer and nut which was
threaded onto the supporting rod
Change in the box beam design:
 The bottom end went through the box beam and attached with a washer and nut
 They then drilled another set of holes, which was offset 4 inches inward along the
axis of the box beam, in the top walkway and hung the other halves of the rods
from the top walkway.
The changed design caused the hotel walkways to collapse. These are the reasons why
the walkways fell.
Reasons why the hotel walkways fell:
 The box beams resting on the supporting rod nuts and washers were deformed
because of the stress that was exerted on them.
 The box beam resting on the nuts and washers on the rods could no longer hold
up the load.
 The box beams (and walkways) separated from the ceiling rods.
 The second and fourth floor walkways fell to the atrium first floor with the fourth
floor walkway coming to rest on top of the second.

9. Stephanie Ulman
Stephanie Ulman Hyatt Assignment 9/10/12
0610 403-02 Failure of Mechanics 9
Figure 11 shows the hanging rod, washer, threads and supporting nut. Also this picture
shows the deformation of the washers.
Figure 12 shows a drawing of the cross section. This is going to fail because the
structure is going to deform when it is under stress.

10. Stephanie Ulman
Stephanie Ulman Hyatt Assignment 9/10/12
0610 403-02 Failure of Mechanics 10
Figure 13 shows an example of what the cross section of the 3rd box beam looked like.
The 3rd box beam was deformed (the flanges have been bent significantly, and the weld
is bowed out.
Figure 14 shows a picture of the cross section of the 4th beam. The box beam is really
deformed and there is a huge gap where the weld is supposed to be.

11. Stephanie Ulman
Stephanie Ulman Hyatt Assignment 9/10/12
0610 403-02 Failure of Mechanics 11
Figure 15 shows another picture of the cross section of the box beam, (the modified
design). This was on the 2nd and 4th floor.
Therefore the box beam is another reason why it failed. The modified box beam was
supporting nuts and washers were deformed because the nut was carrying twice the
amount of stress it was supposed to.
Therefore the box beam and rods could not handle the reaction forces on the nut (also
stress). Therefore the walkways and the box beam separated and the hotel walkways
fell.
Third Problem
In the Hyatt disaster there was communication problems between the fabricator and the
engineers. The fabricators modified the design and the engineers approved the design
without checking it.
The fabricator had modified the design to use two hanging rods and the engineers
approved the change without checking it. Also, the fabricators changed the design of
the box beam too. (As stated above)
The fabricator company name was Havens Steel. The engineering company was
named GCE. Havens Steel modified the drawings and sent to GCE for approval. GCE

12. Stephanie Ulman
Stephanie Ulman Hyatt Assignment 9/10/12
0610 403-02 Failure of Mechanics 12
sent the drawings back to Havens Steel. GCE said that there were miscommunications
because the drawings that where prepared where preliminary sketches and interpreted
by Havens Steel as finalized drawings. An engineer named Jack D. Gillum gave a
sealed of approval was attached to the revised design of the design drawings. So the
communication problem led to confusion about the engineering design. The
communication problems between these two companies had an impact on the collapse
of the walkways in the hotel.
FBD

13. Stephanie Ulman
Stephanie Ulman Hyatt Assignment 9/10/12
0610 403-02 Failure of Mechanics 13

14. Stephanie Ulman
Stephanie Ulman Hyatt Assignment 9/10/12
0610 403-02 Failure of Mechanics 14
The free body diagram shows that all the forces are equal. The forces and stresses that
are on the nuts are different that the forces on the rods. In the modified drawing (the
FBD above the upper nut is going to fail) because the nut is carrying twice the weight
because it is carrying two different rods (walkways).

15. Stephanie Ulman
Stephanie Ulman Hyatt Assignment 9/10/12
0610 403-02 Failure of Mechanics 15
Conclusion:
In conclusion there are many causes why the Hyatt Regency Hotel walkways collapsed.
One of the main causes there was twice the amount of stress on the modified designs.
(These modified designs where on the 2nd and 4th floor.
The box beam is another reason why it failed. The modified box beam supporting nuts
and washers were deformed because the nut was carrying twice the amount of stress it
was supposed to. Therefore the box beam and rods could not handle the reaction
forces on the nut (also stress). Therefore the walkways and the box beam separated
and the hotel walkways fell.
The free body diagram shows that all the forces are equal in the rods. The nuts are not
equal in the modified drawing because in the FBD above the nut has to carry twice the
load. Therefore, this design failed because of all these things so engineers have to
double check their work and have other people check it because thousands of lives can
be in danger if they make a mistake.

16. Stephanie Ulman
Stephanie Ulman Hyatt Assignment 9/10/12
0610 403-02 Failure of Mechanics 16
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